Small and/or compact tractors with internal combustion engines have commonly used downwardly directed exhaust pipes for many applications. Downwardly directed exhaust pipes direct exhaust below the internal combustion engine and are preferred for small and/or compact tractor applications such as mowing, road transport, general field work and work inside buildings. Upwardly directed exhaust pipes direct exhaust up above the engine and are more suited for other applications such as loader work, snow blowing, working in vegetable fields or on sensitive turf grass, working near livestock, or stationary applications including running an aeration pump or grain auger.
Recently, efforts to reduce emissions including Tier 4 regulations have resulted in small and/or compact tractors having elevated exhaust temperatures at certain times. Specifically, emissions reduction devices such as diesel particulate filters (DPFs) periodically result in elevated exhaust temperatures such as approximately 600 degrees C. during regeneration. Other emissions reduction devices or exhaust treatment devices also may result in high exhaust temperatures. However, it is preferred that a small and/or compact tractor's downwardly directed exhaust temperatures should not exceed approximately 200 degrees C., which may be the maximum normal operating temperature of the exhaust.
Attempts to reduce high exhaust temperature down to the normal maximum exhaust temperature of 200 degrees C. have not been successfully implemented in small and/or compact tractors. For example, aspirators and venturis have not been effective because space constraints prevent sizing aspirators and venturis large enough to achieve the 200 degree C. outlet temperature needed for downward exhaust.
A small and/or compact tractor exhaust system is needed to prevent downwardly directed exhaust exceeding 200 degrees C. A system is needed that limits or reduces high temperature downwardly directed exhaust without aspirators or venturis. A system is needed that allows exhaust to exit through downwardly directed exhaust pipes for some applications, and through upwardly directed exhaust pipes for other applications. A system is needed that directs exhaust during high temperature engine regeneration downwardly when safe to do so, and to reduce or minimize operator discomfort.